Conventionally, an electric compressor (hereinafter, simply referred to as a “compressor”), which is an example of a fluid machine, is used as a component for an air-conditioning apparatus, a refrigerating apparatus, a heat pump apparatus for hot water supplier and the like. A typical compressor includes a compressor mechanism and an electric motor. The electric motor is made up of a rotor and a stator, and a main shaft is fixed to the rotor so as to transmit rotation force to the compressor mechanism. The main shaft is fixed to the rotor by shrink-fitting or press-fitting (for example, see Patent Literature 1).
Further, a rotor core, which is a component of the rotor, is made up of a plurality of stacked steel plates. A permanent magnet is embedded in the stacked steel plates, and end plates made of a non-magnetic material are disposed on both ends of the stacked steel plates. The rotor core is often tightened by a rivet that penetrates the end plates and the stacked steel plates. Further, in some cases, a balance weight is disposed on one or both ends of the rotor core, and the end plates, the stacked steel plates, and the balance weight are tightened by the rivet.
In general, a method for improving a machinability of the rotor core is known, in which a plurality of swage sections (close contact portions) are disposed on the steel plate so that the rotor core is made to a unit by press-fitting into the swage sections when the steel plates are stacked.
Further, when the rotor core is tightened by the rivet, in a typically known method, the permanent magnet in each magnetic pole is tightened by one rivet on either of the outer circumferential side in the radial direction or on the inner circumferential side in the radial direction to the permanent magnet (for example, see Patent Literature 2).
Further, a method for improving a machinability in shrink-fitting or press-fitting the main shaft into the rotor core is known, in which the rivets are disposed on each of the outer circumferential side and on the inner circumferential side in the radial direction to the permanent magnet of the rotor core so that the accuracy of the inner diameter cylindricity of the rotor core is improved by adjusting the tightening force (for example, see Patent Literature 3).
Further, as a method for improving a machinability in shrink-fitting or press-fitting the main shaft by improving the accuracy of the inner diameter cylindricity of the rotor core, a configuration in which a metal pipe having a substantially cylindrical shape is inserted into the inner diameter section of the rotor core is known (for example, see Patent Literature 4).